Plasma processing (both etching and depositing) is widely used in the semiconductor industry, and plasma based etching and deposition equipment is widely utilized. Many integrated circuits undergo at least one plasma etch or plasma deposition step during fabrication, and semiconductor based devices, such as pressure sensors, optical detectors for channel optical waveguides and the like, usually undergo a plasma based processing step in their manufacture.
Plasma deposition is often referred to as plasma enhanced chemical vapor deposition (or PECVD). Plasma etching in general encompasses several different processes including conventional plasma etching, reactive ion etching (or RIE), reactive ion beam etching (or RIBE), and down-stream etching, a recently developed process wherein ions are generated in one region of a chamber and utilized for etching in a different region of the chamber. Heretofore known and utilized equipment, however, requires that the entire unit to be processed, for example a wafer, be subjected to processing.
For example, known methods of plasma etching or deposition require that a whole wafer be placed in a small vacuum chamber. The air is pumped out and appropriate gases are admitted into the chamber with very precisely controlled flow rates. A typical plasma processing system includes a pair or parallel electrode plates arranged inside the chamber. The wafer or wafers (often 2 to 6 inch silicon substrates) are placed on one of these plates. The plate is either heated or cooled and a DC or RF generator is utilized to generate a field between the parallel plates. The field ionizes the gases and they either form volatile compounds when impinging on the substrate and thus etch, or they are utilized for deposition of a material on the heated substrate.
While in-situ monitoring of semiconductor device properties during plasma processing would be very desirable in many cases, such is extremely difficult within the confines of a chamber where monitoring equipment is exposed to a volatile chemical and physical environment. In addition, while various devices for performing isolated processing of substrates have been heretofore suggested and/or utilized (see, for example, U.S. Pat. Nos. 4,359,360 and 3,969,813), such heretofore known devices have not provided for plasma processing equipment, have not always proven effective for processing operations requiring controllable etch rates and etch depths of only a small area of an unmasked substrate, and have not provided for access to the substrate for monitoring of device performance parameters during processing and/or etch or deposition control.